Which of the following statements about the 'Jet Stream' are correct? (A) The polar front jet stream flows at an altitude of 9–12 km. (B) The subtropical westerly jet stream is located around 25°–30° N/S latitudes. (C) Jet streams influence the intensity and movement of mid-latitude cyclones. (D) Jet streams are surface-level wind systems. Choose the correct option:

With reference to the Madden-Julian Oscillation (MJO), consider the following statements: I. It is an eastward-moving tropical disturbance rather than a stationary atmospheric trough. II. It is associated with alternating phases of enhanced and suppressed cloudiness, convection and rainfall. III. It generally operates within the tropical belt between 30°N and 30°S latitudes. IV. It can influence monsoon variability as well as tropical cyclone activity. Which of the statements given above are correct?

Which of the following correctly explains the formation of clouds in the atmosphere?